Figure 5 is a speed limit sign from a European motorway. The speeds shown are in km/h (kilometres per hour). (i) The sign tells drivers to drive at a slower speed in wet weather. Explain why it is safer for drivers to drive at a slower speed in wet weather. (ii) Show that a speed of 31 m/s is less than a speed of 130 km/h. (iii) The driver's reaction time is the time between the driver seeing an emergency and starting to brake. A car is travelling at a speed of 31 m/s. The car travels 46 m between the driver seeing an emergency and starting to brake. Calculate the driver's reaction time. Give your answer to 2 significant figures.

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Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

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Figure 5 is a speed limit sign from a European motorway. The speeds shown are in km/h (kilometres per hour). (i) The sign tells drivers to drive at a slower speed i... show full transcript

Worked Solution & Example Answer:Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Step 1

Explain why it is safer for drivers to drive at a slower speed in wet weather.

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Answer

Driving at a slower speed in wet weather is safer for several reasons. Firstly, wet roads reduce friction between the tires and the road, which can lead to slippage. Additionally, reduced visibility in wet conditions can make it harder for drivers to react quickly. This increased stopping distance means that slower speeds allow for more time to react and bring the vehicle to a stop, ultimately reducing the risk of accidents.

Step 2

Show that a speed of 31 m/s is less than a speed of 130 km/h.

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Answer

To compare the speeds, we need to convert 31 m/s into kilometers per hour:

Convert meters per second to kilometers per hour:

$31 ext{ m/s} = 31 \times \frac{3600}{1000} \text{ km/h} = 111.6 \text{ km/h}$
Compare with 130 km/h:

Since 31 m/s is equal to 111.6 km/h, which is less than 130 km/h, we have confirmed that a speed of 31 m/s is less than 130 km/h.

Step 3

Calculate the driver's reaction time.

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Answer

To find the driver's reaction time, we can use the formula:

$\text{Reaction Time} = \frac{\text{Distance}}{\text{Speed}}$

Given that the car travels a distance of 46 meters while travelling at 31 m/s:

$\text{Reaction Time} = \frac{46 \text{ m}}{31 \text{ m/s}} \approx 1.48 \text{ seconds}$

Rounding to 2 significant figures, the driver's reaction time is approximately 1.5 seconds.

Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Worked Solution & Example Answer:Figure 5 is a speed limit sign from a European motorway - Edexcel - GCSE Physics - Question 3 - 2022 - Paper 1

Explain why it is safer for drivers to drive at a slower speed in wet weather.

Show that a speed of 31 m/s is less than a speed of 130 km/h.

Calculate the driver's reaction time.

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